When Hank Aaron broke Babe Ruth's career home run record 31 years ago, baseball fans could watch the instant replay and then look up both players' home run totals in Macmillan's 1000-page Baseball Encyclopedia. Any further analysis of the two home run kings involved a pencil, a scratchpad and a slide rule. But when Barry Bonds of the San Francisco Giants bats for Babe Ruth's record a few weeks from now, it'll be a whole new ballgame for stat-obsessed fans.

This is the best time in history to be a baseball geek. Not only are the game's most hallowed records up for grabs, but technology has made it a cinch to crunch stats. A prime tool for the job is www.baseball-reference.com -- the brainchild of Sean Forman, a 33-year-old assistant professor of mathematics and computer science at Saint Joseph's University in Philadelphia. While avoiding work on his thesis five years ago, Forman grew frustrated with the lack of historical baseball data on the Web.

"I thought there should be a place on the Internet where you could find Ty Cobb's stats fairly easily," Forman recalls. There wasn't, so he designed a site that covers all the bases, so to speak. It holds the records of more than 16,000 players--everyone who played in a major league game; year-by-year team and league pages; and rankings that range from the simple (career home runs) to the arcane (single-season intentional walks).

Want to debunk the conventional wisdom dished out by pundits on bar stools and network TV? This is the place to arm yourself. Just a couple of clicks of the mouse, for instance, reveals that since 1900 there have been only 14 seasons in which a player posted an on-base percentage of over .500 -- and Ruth and Bonds account for nine of them. When it comes to this kind of maneuverability, comparing the power of the Internet to the now out-of-print "Big Mac" encyclopedia is like comparing Bonds's sleek 32-ounce sugar maple Sam Bat to Ruth's bludgeon-like 45-ounce Louisville Slugger.

THE GREAT DEBATE

Who had it easier, Ruth or Bonds? There's no simple answer. Here are four ways baseball has evolved since the 1920s.

Bigger Guns

Weight training and "flaxseed oil" have helped out at the plate. According to www.baseball-reference.com, there were 1.12 homers per game in the 2001 season--three times more than in 1927.

Better Balls

You can't hit what you can't see. Until 1920, baseballs were often covered in tobacco juice. Then Ray Chapman was killed by a pitch, the spitball was replaced by clean, white balls, and home runs took off.

Slicker Pitches

These days, cut fastballs, split-fingers and sliders factor in with situational pitching to keep hitters off their heels. The year 2001 saw 6.67 strikeouts per game--almost 2.5 times more than in 1927.

Smaller Zones

With a 17-in.-wide plate, a 6-ft.-2-in. player in 1927, like Babe Ruth, had a strike zone of roughly 545 sq. in. By 2001, rule changes shrank the zone of a 6-ft.-2-in. player, like Barry Bonds, to about 410 sq. in. -- Davin Coburn

So how do these two elite sluggers stack up statistically? A quick look at the numbers shows that Ruth took fewer games and at-bats than Bonds will have to, to get to 714 home runs. However, Forman insists there's more to the story. "People may have the impression that Ruth played in the dead-ball era," he says, referring to the first two decades of the 20th century, when a softer ball was used, "but he actually played in a better offensive environment than Bonds." His proof? The average hitter during Ruth's day batted .285, while .262 has been the norm during Bonds's career. To build a case for either player with your own stats, you can find raw data at another site, The Baseball Archive (www.baseball1.com).

While analysts point to the many variables that separate the Babe's era from Bonds's, a closer look indicates the two icons may be more alike than different. Both struck out infrequently (Ruth only 89 times in 1927, the year he hit 60 home runs, and Bonds 93 times in 2001, the year he pounded 73); hit for a high average (Ruth went over .300 for 17 seasons, while Bonds has notched .300 for 11 seasons so far); and intimidated pitchers right and left (Bonds and Ruth are first and third on the career walks list, respectively).

"I don't think Bonds is going to have as much historical impact as Ruth or Aaron," Forman proffers. "But the numbers show that Bonds is every bit the hitter that Ruth was."

As soon as Barry Bonds slams that historic homer, pop over to www.baseball-reference.com and begin your own study of these two legendary sluggers. But be forewarned that you won't be the first to do so: Forman reports that Ruth's page has been viewed 890,000 times, while Bonds holds the site's unofficial record with over 1.1 million hits. Web hits, that is.